The present invention relates to systems for protecting an engine upon the occurence of a low oil pressure condition or a high engine temperature condition and, more particularly, to a unique mechanical system including an actuator, a pilot controlled pressure sensor and a temperature sensing valve.
Heretofore, various forms of engine shutdown systems have been proposed. Such systems are primarily adapted for protection of diesel engines in industrial vehicles, trucks and the like. These systems automatically shut down an engine whenever an abnormal operating condition is detected. Such conditions include a dangerously low or a total loss of engine oil pressure and/or a dangerously high engine or engine coolant temperature. In the event of a ruptured oil line or a broken fan belt and other cooling system failures, immediate action must be taken by the vehicle operator if damage to the engine is to be prevented. Failure to notice an abnormal operating condition and/or an intentional refusal to take corrective action are overcome through an automatic shutdown system.
An example of a prior shutdown or engine protection system may be found in commonly owned U.S. Pat. No. 3,602,207 entitled Automatic Override for Engine Safety Shutdown Systems and issued on Aug. 31, 1971 to Kilmer. This commonly owned patent discloses a system including a pressure sensor which senses engine oil pressure and an engine coolant temperature sensor. These sensors are electrical/mechanical devices which control a solenoid operated fuel valve, for example. Each sensor includes a normally closed switch and a normally open switch. Should engine oil pressure drop dangerously low or engine operating temperature rise above an acceptable maximum, the sensors close the engine fuel valve, thereby automatically shutting down the engine. Other systems including similar mechanical and electrical sensors actuate an air solenoid which in turn causes actuation of the shutdown lever on the engine governor box. The system disclosed in U.S. Pat. No. 3,602,207 also incorporates an electronic override circuit which permits engine start-up and also permits restart of the engine for a limited period after automatic shutdown.
Engine protection systems are also desirable for certain industrial applications wherein the engine to be protected does not have its own electrical power supply. Such applications include irrigation systems, mine vehicles and other industrial uses. The system as disclosed in U.S. Pat. No. 3,602,207 would not be usable in such applications.
Other forms of engine protection systems automatically control the flow of air through the coolant radiator in response to engine temperature. A temperature sensor and actuator controls a shutter arrangement mounted on the radiator. An example of such a system may be found in commonly owned U.S. Pat. No. 3,853,269 entitled Temperature Actuated Valve and issued on Dec. 10, 1974 to Graber. Shutter control systems typically use compressed air to actuate the shutters. Some systems use an electric motor for shutter position. Available systems are not useable on engines without compressed air such as found in medium or small delivery vehicles and fixed industrial installations.